Portrait (left side) of the odontostome ciliate, Pelodinium reniforme
(Lauterborn,1908). The genus is monospecific. The cell outline is broadly reniform and laterally compressed. The right surface is slightly convex. The clear rigid pellicle bears inconspicuous longitudinal ribs. A small midline posterior indentation is bordered by 6 short blunt spines (3 each on the right and left surfaces). The cytostome and adoral zone of membranelles are located on the mid-portion of the ventral surface (not seen in this view). There is a prominent sharp tooth-like spine anterior to the cytostome. The frontal zone of kineties (5 single and 2 double rows) wraps from the left surface around the ventrum and onto the right surface to the midline. The somatic ciliature is reduced to 4 right and 3 left longitudinal kineties some of which extend at least Â½ the body length. The ovoid macronucleus may be single or bipartite. There is a single posterior contractile vacuole near the cytostome. There are symbiotic methanogenic bacteria in the cytoplasm. Brownish refractile granules are clustered anteriorly. Collected from hypoxic sediment of standing freshwater near Boise, Idaho February 2004. DIC optics.